Re: [PATCH net-next 2/9] mptcp: track some aggregate data counters

From: Paolo Abeni
Date: Fri Jun 23 2023 - 10:42:15 EST

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Hi,

On Fri, 2023-06-23 at 16:25 +0200, Eric Dumazet wrote:
> On Tue, Jun 20, 2023 at 6:30 PM Matthieu Baerts
> <matthieu.baerts@xxxxxxxxxxxx> wrote:
> >
> > From: Paolo Abeni <pabeni@xxxxxxxxxx>
> >
> > Currently there are no data transfer counters accounting for all
> > the subflows used by a given MPTCP socket. The user-space can compute
> > such figures aggregating the subflow info, but that is inaccurate
> > if any subflow is closed before the MPTCP socket itself.
> >
> > Add the new counters in the MPTCP socket itself and expose them
> > via the existing diag and sockopt. While touching mptcp_diag_fill_info(),
> > acquire the relevant locks before fetching the msk data, to ensure
> > better data consistency
> >
> > Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/385
> > Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
> > Reviewed-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
> > Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
> > ---
> > include/uapi/linux/mptcp.h | 5 +++++
> > net/mptcp/options.c | 10 ++++++++--
> > net/mptcp/protocol.c | 11 ++++++++++-
> > net/mptcp/protocol.h | 4 ++++
> > net/mptcp/sockopt.c | 25 ++++++++++++++++++++-----
> > 5 files changed, 47 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/uapi/linux/mptcp.h b/include/uapi/linux/mptcp.h
> > index 32af2d278cb4..a124be6ebbba 100644
> > --- a/include/uapi/linux/mptcp.h
> > +++ b/include/uapi/linux/mptcp.h
> > @@ -123,6 +123,11 @@ struct mptcp_info {
> > __u8 mptcpi_local_addr_used;
> > __u8 mptcpi_local_addr_max;
> > __u8 mptcpi_csum_enabled;
> > + __u32 mptcpi_retransmits;
> > + __u64 mptcpi_bytes_retrans;
> > + __u64 mptcpi_bytes_sent;
> > + __u64 mptcpi_bytes_received;
> > + __u64 mptcpi_bytes_acked;
> > };
> >
> > /*
> > diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> > index 4bdcd2b326bd..c254accb14de 100644
> > --- a/net/mptcp/options.c
> > +++ b/net/mptcp/options.c
> > @@ -1026,6 +1026,12 @@ u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
> > return cur_seq;
> > }
> >
> > +static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
> > +{
> > + msk->bytes_acked += new_snd_una - msk->snd_una;
> > + msk->snd_una = new_snd_una;
> > +}
> > +
> > static void ack_update_msk(struct mptcp_sock *msk,
> > struct sock *ssk,
> > struct mptcp_options_received *mp_opt)
> > @@ -1057,7 +1063,7 @@ static void ack_update_msk(struct mptcp_sock *msk,
> > __mptcp_check_push(sk, ssk);
> >
> > if (after64(new_snd_una, old_snd_una)) {
> > - msk->snd_una = new_snd_una;
> > + __mptcp_snd_una_update(msk, new_snd_una);
> > __mptcp_data_acked(sk);
> > }
> > mptcp_data_unlock(sk);
> > @@ -1123,7 +1129,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
> > /* on fallback we just need to ignore the msk-level snd_una, as
> > * this is really plain TCP
> > */
> > - msk->snd_una = READ_ONCE(msk->snd_nxt);
> > + __mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
> >
> > __mptcp_data_acked(subflow->conn);
> > mptcp_data_unlock(subflow->conn);
> > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> > index 9c756d675d4d..d5b8e488bce1 100644
> > --- a/net/mptcp/protocol.c
> > +++ b/net/mptcp/protocol.c
> > @@ -377,6 +377,7 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
> >
> > if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) {
> > /* in sequence */
> > + msk->bytes_received += copy_len;
> > WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
> > tail = skb_peek_tail(&sk->sk_receive_queue);
> > if (tail && mptcp_try_coalesce(sk, tail, skb))
> > @@ -760,6 +761,7 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk)
> > MPTCP_SKB_CB(skb)->map_seq += delta;
> > __skb_queue_tail(&sk->sk_receive_queue, skb);
> > }
> > + msk->bytes_received += end_seq - msk->ack_seq;
> > msk->ack_seq = end_seq;
> > moved = true;
> > }
> > @@ -1531,8 +1533,10 @@ static void mptcp_update_post_push(struct mptcp_sock *msk,
> > * that has been handed to the subflow for transmission
> > * and skip update in case it was old dfrag.
> > */
> > - if (likely(after64(snd_nxt_new, msk->snd_nxt)))
> > + if (likely(after64(snd_nxt_new, msk->snd_nxt))) {
> > + msk->bytes_sent += snd_nxt_new - msk->snd_nxt;
> > msk->snd_nxt = snd_nxt_new;
> > + }
> > }
> >
> > void mptcp_check_and_set_pending(struct sock *sk)
> > @@ -2590,6 +2594,7 @@ static void __mptcp_retrans(struct sock *sk)
> > }
> > if (copied) {
> > dfrag->already_sent = max(dfrag->already_sent, info.sent);
> > + msk->bytes_retrans += copied;
> > tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
> > info.size_goal);
> > WRITE_ONCE(msk->allow_infinite_fallback, false);
> > @@ -3102,6 +3107,10 @@ static int mptcp_disconnect(struct sock *sk, int flags)
> > WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
> > mptcp_pm_data_reset(msk);
> > mptcp_ca_reset(sk);
> > + msk->bytes_acked = 0;
> > + msk->bytes_received = 0;
> > + msk->bytes_sent = 0;
> > + msk->bytes_retrans = 0;
> >
> > WRITE_ONCE(sk->sk_shutdown, 0);
> > sk_error_report(sk);
> > diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> > index 47b46602870e..27adfcc5aaa2 100644
> > --- a/net/mptcp/protocol.h
> > +++ b/net/mptcp/protocol.h
> > @@ -262,10 +262,13 @@ struct mptcp_sock {
> > u64 local_key;
> > u64 remote_key;
> > u64 write_seq;
> > + u64 bytes_sent;
> > u64 snd_nxt;
> > + u64 bytes_received;
> > u64 ack_seq;
> > atomic64_t rcv_wnd_sent;
> > u64 rcv_data_fin_seq;
> > + u64 bytes_retrans;
> > int rmem_fwd_alloc;
> > struct sock *last_snd;
> > int snd_burst;
> > @@ -274,6 +277,7 @@ struct mptcp_sock {
> > * recovery related fields are under data_lock
> > * protection
> > */
> > + u64 bytes_acked;
> > u64 snd_una;
> > u64 wnd_end;
> > unsigned long timer_ival;
> > diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> > index e172a5848b0d..fa5055d5b029 100644
> > --- a/net/mptcp/sockopt.c
> > +++ b/net/mptcp/sockopt.c
> > @@ -889,7 +889,9 @@ static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
> >
> > void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
> > {
> > + struct sock *sk = (struct sock *)msk;
> > u32 flags = 0;
> > + bool slow;
> >
> > memset(info, 0, sizeof(*info));
> >
> > @@ -898,6 +900,9 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
> > info->mptcpi_add_addr_accepted = READ_ONCE(msk->pm.add_addr_accepted);
> > info->mptcpi_local_addr_used = READ_ONCE(msk->pm.local_addr_used);
> >
> > + if (inet_sk_state_load(sk) == TCP_LISTEN)
> > + return;
> > +
> > /* The following limits only make sense for the in-kernel PM */
> > if (mptcp_pm_is_kernel(msk)) {
> > info->mptcpi_subflows_max =
> > @@ -915,11 +920,21 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
> > if (READ_ONCE(msk->can_ack))
> > flags |= MPTCP_INFO_FLAG_REMOTE_KEY_RECEIVED;
> > info->mptcpi_flags = flags;
> > - info->mptcpi_token = READ_ONCE(msk->token);
> > - info->mptcpi_write_seq = READ_ONCE(msk->write_seq);
> > - info->mptcpi_snd_una = READ_ONCE(msk->snd_una);
> > - info->mptcpi_rcv_nxt = READ_ONCE(msk->ack_seq);
> > - info->mptcpi_csum_enabled = READ_ONCE(msk->csum_enabled);
> > + mptcp_data_lock(sk);
> > + info->mptcpi_snd_una = msk->snd_una;
> > + info->mptcpi_rcv_nxt = msk->ack_seq;
> > + info->mptcpi_bytes_acked = msk->bytes_acked;
> > + mptcp_data_unlock(sk);
> > +
> > + slow = lock_sock_fast(sk);
>
> This causes a lockdep issue.
>
> lock_sock_fast(sk) could sleep, if socket lock is owned by another process.
>
> But we are called from a context where both a spin lock and
> rcu_read_lock() are held.
>
> BUG: sleeping function called from invalid context at net/core/sock.c:3549
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 316, name: syz-executor.4
> preempt_count: 1, expected: 0
> RCU nest depth: 1, expected: 0
> 7 locks held by syz-executor.4/316:
> #0: ffffffff8e125408 (sock_diag_mutex){+.+.}-{3:3}, at:
> sock_diag_rcv+0x1b/0x40 net/core/sock_diag.c:279
> #1: ffffffff8e125588 (sock_diag_table_mutex){+.+.}-{3:3}, at:
> sock_diag_rcv_msg net/core/sock_diag.c:259 [inline]
> #1: ffffffff8e125588 (sock_diag_table_mutex){+.+.}-{3:3}, at:
> sock_diag_rcv_msg+0x2d2/0x440 net/core/sock_diag.c:248
> #2: ffff8880232bb688 (nlk_cb_mutex-SOCK_DIAG){+.+.}-{3:3}, at:
> netlink_dump+0xbe/0xc50 net/netlink/af_netlink.c:2215
> #3: ffffffff8e29a628 (inet_diag_table_mutex){+.+.}-{3:3}, at:
> inet_diag_lock_handler+0x6e/0x100 net/ipv4/inet_diag.c:63
> #4: ffffffff8c7990c0 (rcu_read_lock){....}-{1:2}, at:
> mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:95 [inline]
> #4: ffffffff8c7990c0 (rcu_read_lock){....}-{1:2}, at:
> mptcp_diag_dump+0x7c8/0x1330 net/mptcp/mptcp_diag.c:197
> #5: ffffc90001316bf0 (&h->lhash2[i].lock){+.+.}-{2:2}, at: spin_lock
> include/linux/spinlock.h:350 [inline]
> #5: ffffc90001316bf0 (&h->lhash2[i].lock){+.+.}-{2:2}, at:
> mptcp_diag_dump_listeners net/mptcp/mptcp_diag.c:98 [inline]
> #5: ffffc90001316bf0 (&h->lhash2[i].lock){+.+.}-{2:2}, at:
> mptcp_diag_dump+0x838/0x1330 net/mptcp/mptcp_diag.c:197
> #6: ffff88802c42a5f0 (msk_lock-AF_INET){+.+.}-{0:0}, at:
> mptcp_diag_get_info+0x1ae/0x380 net/mptcp/mptcp_diag.c:224
> Preemption disabled at:
> [<0000000000000000>] 0x0

Thank you for the report.

out-of-order patches here. "mptcp: track some aggregate data counters"
should have landed to net-next only after:

57fc0f1ceaa4 mptcp: ensure listener is unhashed before updating the sk
status

The latter should explicitly avoid the critical scenario above. Anyhow
the current net-next tree (after merging back net) should be ok (at
least I can't repro the issue here).

Thanks,

Paolo

Next message: Laurent Pinchart: "Re: [PATCH 01/39] dt-bindings: display: Add Renesas SH-Mobile LCDC bindings"
Previous message: Jim Quinlan: "[PATCH v6 5/5] PCI: brcmstb: Remove stale comment"
In reply to: Eric Dumazet: "Re: [PATCH net-next 2/9] mptcp: track some aggregate data counters"
Next in thread: Matthieu Baerts: "[PATCH net-next 5/9] mptcp: introduce MPTCP_FULL_INFO getsockopt"
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